ISRO Halts Semi-Cryogenic Engine Hot Test Midway

The Indian Space Research Organisation (ISRO) recently encountered a setback in their semi-cryogenic engine development project. During a scheduled hot test, the engine’s performance unexpectedly deviated from expectations, leading to the termination of the test.

On July 1, 2023, ISRO announced that they had initiated the first hot test on an intermediate configuration of the semi-cryogenic engine known as the Power Head Test Article (PHTA). The test took place at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu.

ISRO’s ultimate objective is to create a 2000 kN thrust semi-cryogenic engine that will power the booster stages of future launch vehicles.

Initially, the test progressed as planned, with the PHTA igniting and performing as expected for 1.9 seconds. However, at the 2-second mark, there was a sudden surge in turbine pressure followed by a decrease in turbine speed. In response to this unforeseen development, ISRO decided to terminate the test for safety reasons.

ISRO stated, “At 2.0 seconds, an unanticipated spike in the turbine pressure and subsequent loss of turbine speed was observed. As a precautionary measure, the test was terminated. Further analysis is underway to gain a better understanding before proceeding with longer duration hot tests.”

The primary goal of the test was to evaluate the joint performance of critical subsystems such as the gas generator, turbo pumps, pre-burner, and control components. This was achieved through a brief 4.5-second hot-firing. The focus was on assessing the ignition and production of hot gas within the pre-burner chamber, which drives the primary turbine responsible for fuel and oxidizer pumps.

The semi-cryogenic engine uses a propellant mixture of Liquid Oxygen (LOX) and Kerosene. The PHTA represents the initial hardware test within the larger engine development program.

The test was conducted at a dedicated facility at IPRC specifically designed for testing semi-cryogenic engines and stages. Testing of the PHTA began at this facility in May 2023. The findings from the truncated test and subsequent analysis will guide future hot tests of longer durations.